Editing Willis Tower (section)

==== Early construction ====
[[File:Sears Willis Tower.jpg|thumb|upright|The Sears Tower (now the Willis Tower) during its construction in 1973]]

Work on the building's foundation commenced in August 1970. Contractors excavated the lot to a depth of {{convert|50|ft}}, and they removed {{convert|180000|ft3}} of dirt from the site.<ref name="p169075911">{{Cite news |date=April 18, 1971 |title=Build Foundation of Huge Sears Tower |page=D1 |work=Chicago Tribune |id={{proQuest|169075911}}}}</ref> By that November, Spencer, White & Prentis Inc. was excavating a trench around the site, measuring {{convert|60|ft}} deep and {{convert|20|by|216|ft}} across. The contractors then built a [[slurry wall]] within the trench, made of concrete and reinforced steel.<ref name="n109124635">{{Cite news |date=November 22, 1970 |title=New Methods Speed Construction |pages=105 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109124635/new-methods-speed-construction/ |access-date=September 7, 2022}}</ref> Workers used steel bracing to prevent the slurry wall from collapsing inward, then used [[Caisson (engineering)|caissons]] to drill 201 holes into the ground. They also rerouted a sewer that had run underneath Quincy Street, which was to be closed permanently as part of the tower's construction.<ref name="p169075911" />

The [[Diesel Construction Company]] was hired as the Sears Tower's [[general contractor]].<ref name=p133809828/> Sears, Roebuck & Co. chairman [[Gordon M. Metcalf]] installed the building's first steel beam at a ceremony on June 7, 1971.<ref name="n109125056">{{Cite news |date=June 8, 1971 |title=Set First Sears Tower Steel |pages=53 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109125056/set-first-sears-tower-steel/ |access-date=September 7, 2022}}</ref><ref name="nyt-1971-06-08">{{Cite news |date=June 8, 1971 |title=First Steel in Sears Building |language=en-US |work=The New York Times |url=https://www.nytimes.com/1971/06/08/archives/first-steel-in-sears-building.html |access-date=September 7, 2022 |issn=0362-4331}}</ref> The project employed 2,000 workers. To accelerate the building's construction, a concrete plant was built in the building's basement, allowing workers to pour one-third of a concrete floor every day. Contractors built two temporary kitchens on the site for workers, and telephone and loudspeaker systems were installed on every floor to allow workers to communicate. In addition, contractors installed temporary generators that could supply up to {{convert|14000|kW}} simultaneously; during the winter, most of this electricity was used to heat the exposed steel beams on the lowest five floors.<ref name="n109125194">{{Cite news |date=October 3, 1971 |title=Sears Tower Uses Unique New Systems |pages=97 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109125194/sears-tower-uses-unique-new-systems/ |access-date=September 7, 2022}}</ref>